I. Field of the Invention
The present invention relates to the control of the impacts following the variations of a torque set-point to be applied to the wheels.
A particularly interesting application of the invention relates to automatic transmissions, in particular so-called pulsed transmissions, BCI, so-called automatic transmissions, BVA, and so-called robotized transmissions, BVR, but also continuously variable transmissions, CVT, and infinitely variable transmissions, IVT, and hybrid transmissions.
II. Description of Related Art
A motor vehicle automatic transmission conventionally comprises a control block receiving one or more input parameters interpreting, among other things, the wishes of the driver. Then, according to the values of these parameters, the control block delivers a control set-point intended for the wheels of the motor vehicle.
Also, document FR-A-2 827 339, filed in the name of the Applicant, discloses a device for controlling the operating point of a power train intended for a motor vehicle. This device has in particular a module for interpreting the wishes of the driver called IVC module, which generates a torque set-point to be applied to the wheel intended for a block for optimizing the operating point of the power train, called OPF module.
The IVC module determines the torque set-point according to the wishes of the driver, the characteristics of the motor vehicle and its environment.
The impacts, felt by the passengers of a motor vehicle, are due to a jump in the torque set-point, which changes sign on transitions from an acceleration phase to a deceleration phase, for example. This change of sign causes a tipping movement of the power train, reflected for the passengers of the motor vehicle in jerks or impacts with respect to the driver.
In practice, most power trains have two fixing points on the body of the motor vehicle. These allow it to move between two extreme positions, according to whether the motor vehicle is accelerating or decelerating. Alternating acceleration and deceleration phases causes the power train to tip to one of these two positions to compensate for the play of the transmission assembly including that of the automatic transmission. This movement generates impacts transmitted to the driver through the chassis of the motor vehicle.
In order to limit the jerks and impacts, the invention proposes to adapt said torque set-point to be applied to the wheels.
Already known from the state of the art are methods and associated devices with which to make corrections to try to limit, or even eliminate, the impacts. They propose adjusting the parameters controlling the operation of a power train in order to limit the impact of its tipping.
Thus, document FR-2 681 908 discloses a device that can correct control parameters of an internal combustion engine, based on a model estimating the engine torque and a model estimating the transmission for each gear ratio. This device determines the correction to be applied to the engine torque.
Also known from document FR-2 724 432 is a method of correcting the oscillations of the motor vehicle. This method consists in generating a correction value to be applied to the engine torque, based on a variable determined relative to the angular position of the crankshaft.
The corrections made by these two devices relate to the engine torque. However, on most motor vehicles, the tipping of the power train is reflected more particularly in abrupt variations of the torque to be applied to the wheels of the motor vehicle. Given that this zone of variation in the torque set-point to be applied to the wheels of the motor vehicle does not necessarily correspond to the zone of variation of the engine torque about the zero value, the impacts cannot be limited optimally by adding a correction to this engine torque.
Also known, from document GB-2 368 406, is a method for controlling the changes of sign of the output torque set-point of the power train. These are performed when the motor vehicle reaches the desired speed. The control described by document GB-2 368 406 makes it possible to avoid the impacts due to the transition.